Marijuana, Pregnancy, and Breastfeeding

The legal status of cannabis (tetrahydrocannabinol, THC) is going through big changes in North America. 25 states allow marijuana for medical use. It cannot be prescribed by a doctor, but instead is given to patients by medical cannabis dispensaries. As for recreational marijuana, the states of Colorado, Oregon, Alaska, and Washington have permitted its use by adults, and the number of marijuana permissive states is in the process of expanding due to election ballot measures that passed recently in Massachusetts, California, Nevada, and Maine, all of which voted to legalize recreational marijuana. In the same election, North Dakota, Florida, Arkansas, and Montana all voted to begin allowing medical cannabis. All of this is happening in a culture that is evolving to be increasingly open-minded about pot use.

Marijuana has always been available for those who have wanted it but, with legalization, one who may have avoided it before, now can it get it with no fear of arrest, while others who have been using it feel more free to speak their minds about the benefits of cannabis. This is particularly true when it comes to the medicinal properties of cannabis, such as its effects against nausea and pain. In short, the stigma once attached to marijuana use is disappearing and we’re hearing about pot usage by groups of people that a generation ago would have been very silent about. One such group is women who are pregnant or breastfeeding. In the years since marijuana legalization came into effect in Colorado and Washington, it has become clear that about 4 percent of pregnancies occur in women who use marijuana regularly throughout pregnancy. A somewhat higher number of mothers are estimated to use marijuana while breastfeeding, but the numbers are modest compared tobacco, which is smoked by 12-20 percent of pregnant women. On the other hand, the numbers of pregnant pot users, while relatively low, are thought to be up, compared with what they were prior to legalization.

At the same time, there is a great deal of misinformation circulating in connection with THC and its effects during pregnancy. The issue has been covered before on The Pulse, but it’s important enough to warrant a follow up now. As with the effects of pot on the brains of teens, the public conversation is influenced by individuals who argue from what they see as a moral stance, and tend to exaggerate what is known or suspected about the effects of THC on the brain. At the other end of the spectrum are the pro- marijuana activists who exaggerate any benefits that THC may provide, downplay studies revealing possible dangers of the drug, and take results of studies conducted not in a clinical setting but on laboratory cell cultures out of context.

One classic example involves studies that have demonstrated a killing effect of THC on certain types of cancer cells grown in laboratory plates. On more than one occasion, marijuana activists have cited such studies to support a claim that THC fights cancer. It would not be an exaggeration to say that this a frequent talking point for such individuals. Making that point, however, they ignore the fact that we would never apply such a low standard to the evaluation of evidence regarding any other chemical agent that may kill cancer cells. In the development of new anti-cancer drugs, the demonstration of a killing effect in vitro –in a laboratory vessel, such as a plate, or Petri dish—is but an early step in the research. From there, one needs to test the drug in vivo in laboratory animals, and then on human patients in clinical studies. Only a small percentage of agents showing promise in cell culture make it to and through the clinical trial stages.

Where are pregnant women getting the idea to use cannabis? Investigations thus far suggest that often it is the women themselves who decide to use smoke marijuana, or to ingest it within edible sources, such as pot cookies, candies, or brownies. In some cases, they are doing it after consulting with a midwife who gave the green light after the patient indicated that she really wanted to use the drug. In both of these situations, the most common motivation appears to be a desire to eliminate the nausea that comes during the first trimester of pregnancy. However, there is a subset of pregnant women who simply enjoy getting high and don’t want to put a hold on this for 40 weeks. It’s also possible that some marijuana usage during pregnancy is actually the result of encouragement by some practitioners of alternative health care and that the patient would otherwise not have used it. As for pot use in women who are breastfeeding, rather than wanting to eliminate nausea, here the motivation is often the development of post-partum depression, or post-partum anxiety, and the expectation that the THC will prove an effective treatment.

So, what does science have to say about the dangers and benefits? Unfortunately, the bottom line is that there are many uncertainties. Studies have been few, generally involving small numbers of women, and notoriously difficult to control for numerous factors that could confuse the outcome. Women who use THC tend also to be tobacco users, which means we have to take most study results with a big grain of salt. Early indications from laboratory animals studies do suggest, however, that THC can have a very negative effect on fetal brain development, particularly when it comes to the forebrain –that’s the part of the brain that you use to think. There is also some concern about THC and low birth weight. Unlike fetal alcohol syndrome and many effects of tobacco on the newborn, effects of THC consumed during pregnancy may present in more subtle ways, and later in a child’s life. Expanding on animal studies to test clinically for negative consequences of drug is very difficult. Generally, it requires a large population of women using the drug during pregnancy for a generation or more, as happened with tobacco and alcohol.

As for breastfeeding, studies are ongoing. A study, for instance, is looking at lactating women who are taking specific doses of THC and pumping out their milk, which then gets sent for laboratory analysis, while the children born from the volunteers are nourished safely with infant formula. Meanwhile, however, there have been some initial studies suggesting that TCH not only makes its way into breast milk, but, much like nicotine, is concentrated in the milk.

Where does all of this mean for you if you are pregnant and considering using marijuana, either for nausea or pure recreation? The safe route would be don’t do it. Put the bong away for the duration of the pregnancy, until more is known, but realize that not enough will be known before you give birth. Science doesn’t operate that quickly. When confronted with an individual who claims to be an authority, and who suggests that marijuana should be safe, since there is not any strong evidence that it does harm, consider whether that same individual would present a similar attitude if asked about a new pharmaceutical. And finally, if after putting off marijuana throughout pregnancy, if you find that you need it after giving birth, do not take on the role of breastfeeding. With all the unknowns floating around, comfort yourself remembering what we know for certain, that infant formula that you buy at the store is guaranteed not to contain THC.

Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.